The approach to landing and touch down on the runway of an aircraft is probably the most challenging task a pilot undertakes during normal operation. To perform the landing properly, the aircraft approaches the runway within an envelope of attitude, course, speed, and rate of descent limits. The course limits include, for example, both lateral limits and glide slope limits. An approach outside of this envelope can result in an undesirable positioning of the aircraft with respect to the runway, resulting in possibly discontinuance of the landing attempt.
In some instances visibility may be poor during approach and landing operations, resulting in what is known as instrument flight conditions. During instrument flight conditions, pilots rely on instruments, rather than visual references, to navigate the aircraft. Even during good weather conditions, pilots typically rely on instruments to some extent during the approach. Many airports and aircraft include runway assistance landing systems, for example an Instrument Landing System (ILS), to help guide aircraft during approach and landing operations. These systems allow for the display of a lateral deviation indicator to indicate aircraft lateral deviation from the approach course, and the display of a glide slope indicator to indicate vertical deviation from the glide slope.
Because of poor ground infrastructure, there are limits to how low a pilot may descend on approach prior to making visual contact with the runway environment for runways having an instrument approach procedure. Typical low visibility approaches require a combination of avionics equipage, surface infrastructure, and specific crew training. These requirements limit low visibility approaches to a small number of runways. For example, typical decision heights above ground (whether to land or not) for a Non-Directional beacon (NDB) approach is 700 feet above ground, while a VHF Omni-directional radio Range (VOR) approach is 500 feet, a Global Positioning System (GPS) approach is 300 feet, Local Area Augmentation System (LAAS) is 250 feet, and an ILS approach is 200 feet. A sensor imaging system may allow a descent below these altitude-above-ground figures, for example, 100 feet lower on an ILS approach, because the pilot is performing as a sensor, thereby validating position integrity by seeing the runway environment. However, aircraft having an imaging system combined with a heads up display are a small percentage of operating aircraft, and there is a small percentage of runways with the ILS and proper airport infrastructure (lighting and monitoring of signal).
Synthetic vision systems are currently certified for situation awareness purposes in commercial and business aviation applications with no additional landing credit for going below published minimum. Such a display system, when used in conjunction with flight symbology such as on a head-up display system, is known to improve a pilot's overall situational awareness and reduce flight technical errors. However, two concerns related to a synthetic vision system are 1) the lacking of or insufficient separated integrity verification for the displayed information, and 2) the lack of sufficient integrity or short-term critical availability during the final approach phase of data sources used to generate the visual display elements for navigation and verification purposes.
Accordingly, it is desirable to provide a system and method for improving the ability to fly low altitude, low visibility approaches including displaying information supporting a pilot's ability to fly a stabilized approach. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.